Interlaced scanning schemes have been widely adopted in current display monitor systems, including television systems. In a typical interlaced system, the sequence of video fields alternates between odd fields (e.g., fields containing odd numbered lines) and even fields (e.g., fields containing even numbered lines). A conventional display monitor receiving the sequence of fields reproduces each video field in the sequence. Each field is displayed on the display screen, such as a television. For example, first an odd field is displayed, using the odd-numbered scan lines, and then an even field is displayed using the even-numbered scan lines, and so on.
There many disadvantages to this type of interlace system, such as edge flicker, line flicker and line crawling. Furthermore, as the demand of using large screen displays increases, these problems have become more critical. An interlace to non-interlace conversion is a very good solution to remove such problems.
An interlace to non-interlace conversion involves generating a missing line between two adjacent lines in an interlaced signal. Motion adaptive interlace to non-interlace conversion is widely used in current available interlace to non-interlace converters. In such converters, every pixel is classified as a motion or static pixel. For each static pixel, field insertion is executed to generate the missing pixel since there is no motion between consecutive fields. The same vertical resolution will be kept for the static portion of the picture. For each motion pixel, intra-field interpolation is executed to generate the missing pixel.
Normally, most converters only utilize vertical interpolation for the intra-field interpolation. There is no motion effect for the motion portion of the picture. However, jagged edges may result for image objects having diagonal edges. Jagged edges resulting from interpolation are a visually annoying defect, and can sometimes occur to a degree worse than that on an interlaced display. Processing a display signal using edge-adaptive interpolation can eliminate or reduce jagged edge defects that can result from the motion adaptive interlace-to-progressive conversion of prior art systems. An edge adaptive interpolation will solve this problem by performing the interpolation along the edge direction.
In order to perform interpolation along an edge direction, the manner of detecting the edge direction that passes through the missing pixel is important. Edge adaptive interpolation along an image object's edge involves correctly determining the direction of an edge passing through a missing pixel (a pixel that will be generated to form the interpolated line between existing adjacent lines in the interlace signal being converted). Previous methods have utilized various “window” sizes to detect the possible edge directions. For example, some systems utilize a “3×2” window around a missing pixel, which allows only three (3) possible directions to be detected. Other methods have used as large as a “7×2” window which provides seven (7) possible directions to be detected. One example of such a method is described in U.S. patent application Ser. No. 10/154,628, entitled “Method and System for Edge-Adaptive Interpolation for Interlace-to-Progressive Concern,” which is assigned to the present assignee and which is fully and completely incorporated herein by reference. It will be appreciated by those skilled in the art that the computation required for a “7×2” window is much higher than that for a “3×2” window. That is, the larger the window size, the more computation power needed. Additionally, with a larger window size, there exists a greater possibility of false edge direction detection. Once a false edge direction has occurred, a visually annoying dot may appear on the interpolated picture.
As a result, some prior edge adaptive interpolation methods only employ a “3×2” window to minimize the computation power and also the possibility of false detection. But with a “3×2” window, the interpolation can vary only along 45 degree, 90 degree and 135 degree directions. The result will exhibit aliasing, i.e., most of the edge will still appear jagged. Methods utilizing a “7×2” window provide some improvement over convention “3×2” systems. However, even these improved methods perform detection based around a single pixel or point, without efficiently utilizing neighboring information that can increase the accuracy of the detection process.
The present invention provides an improvement over these prior edge adaptive interpolation methods and systems. Particularly, the present invention provides an improved system and method, which utilizes a “9×2” window around a pixel, along with information from neighboring pixels to provide edge-adaptive interpolation.